Optical illusions show vision in a new light

ScienceDaily (2011-03-15) -- Optical illusions have fascinated humans throughout history. Greek builders used an optical illusion to ensure that that their columns appeared straight (they built them with a bulge) and we are all intrigued by the mental flip involved in the case of the young girl/old woman faces. New research demonstrates a more serious use of these illusions in understanding how the brain assesses relative size.